1. Field of the Invention
The present invention relates to a head positioning device which is applied to, for example, a servo track writer for writing servo information onto a magnetic disk as a recording medium.
2. Related Background Art
With the advance of a larger memory capability and a compact design in computers, there is a growing demand for high density in a magnetic disk employed as a recording medium in computers. The magnetic disks need servo information written thereon in advance. An area having servo information written is called a servo track in a magnetic disk. A manufacturing apparatus for writing the servo track is also required to have high accuracy, with the advance of high density in magnetic disk.
FIG. 1 illustrates a conventional apparatus for such a servo track writer. This apparatus comprises a high-precision frequency-stabilized laser light source 1a, a reflection mirror 2, a beam splitter 3, a head arm 4 of a magnetic disk, corner cubes 5a, 5b, a magnetic head 6, a magnetic disk 7, a photoreceiver 8, a control circuit 9, a drive motor 10 for driving the head arm 4 and a casing 11 for housing the magnetic disk.
The laser light source 1a, the beam splitter 3, the corner cubes 5a, 5b and the photoreceiver 8 constitute a laser interferometer. The writing position (position along a radial direction of the magnetic disk 7) of the magnetic head 6 is controlled so that the photoreceiver 8 detects a displacement of the corner cube 5b mounted on the head arm 4 and the control circuit 9 controls the head arm driving motor 10 until the angle of rotation of the motor 10 agrees with a predetermined angle. The magnetic disk 7 is rotated on its own center by a drive motor (not shown), and a plurality of concentric servo tracks are formed by the magnetic head 6.